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<title>Debugging with GDB: Aliases</title>

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<a name="Aliases"></a>
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<p>
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<hr>
<a name="Creating-new-spellings-of-existing-commands"></a>
<h3 class="section">23.6 Creating new spellings of existing commands</h3>
<a name="index-aliases-for-commands"></a>

<p>It is often useful to define alternate spellings of existing commands.
For example, if a new <small>GDB</small> command defined in Python has
a long name to type, it is handy to have an abbreviated version of it
that involves less typing.
</p>
<p><small>GDB</small> itself uses aliases.  For example &lsquo;<samp>s</samp>&rsquo; is an alias
of the &lsquo;<samp>step</samp>&rsquo; command even though it is otherwise an ambiguous
abbreviation of other commands like &lsquo;<samp>set</samp>&rsquo; and &lsquo;<samp>show</samp>&rsquo;.
</p>
<p>Aliases are also used to provide shortened or more common versions
of multi-word commands.  For example, <small>GDB</small> provides the
&lsquo;<samp>tty</samp>&rsquo; alias of the &lsquo;<samp>set inferior-tty</samp>&rsquo; command.
</p>
<p>You can define a new alias with the &lsquo;<samp>alias</samp>&rsquo; command.
</p>
<dl compact="compact">
<dd>
<a name="index-alias"></a>
</dd>
<dt><code>alias [-a] [--] <var>ALIAS</var> = <var>COMMAND</var></code></dt>
</dl>

<p><var>ALIAS</var> specifies the name of the new alias.
Each word of <var>ALIAS</var> must consist of letters, numbers, dashes and
underscores.
</p>
<p><var>COMMAND</var> specifies the name of an existing command
that is being aliased.
</p>
<p>The &lsquo;<samp>-a</samp>&rsquo; option specifies that the new alias is an abbreviation
of the command.  Abbreviations are not shown in command
lists displayed by the &lsquo;<samp>help</samp>&rsquo; command.
</p>
<p>The &lsquo;<samp>--</samp>&rsquo; option specifies the end of options,
and is useful when <var>ALIAS</var> begins with a dash.
</p>
<p>Here is a simple example showing how to make an abbreviation
of a command so that there is less to type.
Suppose you were tired of typing &lsquo;<samp>disas</samp>&rsquo;, the current
shortest unambiguous abbreviation of the &lsquo;<samp>disassemble</samp>&rsquo; command
and you wanted an even shorter version named &lsquo;<samp>di</samp>&rsquo;.
The following will accomplish this.
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) alias -a di = disas
</pre></div>

<p>Note that aliases are different from user-defined commands.
With a user-defined command, you also need to write documentation
for it with the &lsquo;<samp>document</samp>&rsquo; command.
An alias automatically picks up the documentation of the existing command.
</p>
<p>Here is an example where we make &lsquo;<samp>elms</samp>&rsquo; an abbreviation of
&lsquo;<samp>elements</samp>&rsquo; in the &lsquo;<samp>set print elements</samp>&rsquo; command.
This is to show that you can make an abbreviation of any part
of a command.
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) alias -a set print elms = set print elements
(gdb) alias -a show print elms = show print elements
(gdb) set p elms 20
(gdb) show p elms
Limit on string chars or array elements to print is 200.
</pre></div>

<p>Note that if you are defining an alias of a &lsquo;<samp>set</samp>&rsquo; command,
and you want to have an alias for the corresponding &lsquo;<samp>show</samp>&rsquo;
command, then you need to define the latter separately.
</p>
<p>Unambiguously abbreviated commands are allowed in <var>COMMAND</var> and
<var>ALIAS</var>, just as they are normally.
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) alias -a set pr elms = set p ele
</pre></div>

<p>Finally, here is an example showing the creation of a one word
alias for a more complex command.
This creates alias &lsquo;<samp>spe</samp>&rsquo; of the command &lsquo;<samp>set print elements</samp>&rsquo;.
</p>
<div class="smallexample">
<pre class="smallexample">(gdb) alias spe = set print elements
(gdb) spe 20
</pre></div>

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